The present invention relates to a radiation image information recording and reading apparatus which is capable of recording a radiation image on two stimulable phosphor sheets whose ends are superimposed on each other.
Recently there have recently been developed radiation image information recording and reproducing systems for recording the radiation image of an object, such as a human body, on a stimulable phosphor sheet. Such devices scan the stimulable phosphor sheet with stimulating light to cause it to emit light, photoelectrically read the emitted light to produce an image signal, and processing the image signal to obtain a radiation image of the object which may be used for medical diagnosis (see, for example, Japanese Laid-Open Patent Publications Nos. 55-12429, 56-11395, 55-163472, 56-104645, 55-116340, etc).
In these radiation image information recording and reproducing systems, the final radiation image may be reproduced as either a hard copy image or a visible image on a CRT. The stimulable phosphor sheet employed in those systems is not a final image carrier for recording image information, but a temporary image carrier from which image information will eventually be transferred to a suitable recording medium. Therefore, the stimulable phosphor sheet may be repeatedly used, and such repeated use of the stimulable phosphor sheet is highly economical.
In order to use a stimulable phosphor sheet again, any residual radiation energy that may remain on the stimulable phosphor sheet from which the emitted light has been read is discharged according to the process disclosed in Japanese Laid-Open Patent Publications Nos. 56-11392 and 56-12599, for example. After the residual radiation image has been erased, the stimulable phosphor sheet may be used for recording additional radiation images.
There has been proposed a built-in type radiation image information recording and reading apparatus in which a stimulable phosphor sheet is circulated for repetitive use, as disclosed in Japanese Laid-Open Patent Publication No. 59-192240. More specifically, the proposed apparatus utilizes a circulatory feed mechanism for feeding, along a circulatory path, a stimulable phosphor sheet which can record a radiation image. An image recording unit is disposed in the circulatory path for applying a radiation bearing radiation image information of an object to the stimulable phosphor sheet so as to record the radiation image information on the stimulable phosphor sheet. An image reading unit is also disposed in the circulatory path and includes a stimulating light source for emitting stimulating light to scan the stimulable phosphor sheet on which the radiation image information has been recorded by the image recording unit. A photoelectric reading device reads light emitted from the stimulable phosphor sheet scanned by the stimulating light to produce an image signal indicative of the recorded radiation image information, and an erasing unit is disposed in the circulatory path for discharging any residual radiation energy from the stimulable phosphor sheet before new radiation image information is recorded on the stimulable phosphor sheet and after the previous radiation image information has been read by the photoelectric reading means. The stimulable phosphor sheet is circulated along the circulatory path through the image recording unit, the image reading unit, and the erasing unit for repetitive use.
The proposed radiation image information recording and reading apparatus allows successive items of radiation image information to be recorded and read efficiently.
The built-in type radiation image information recording and reading apparatus is designed to record radiation image information with respect to various body parts of patients, including the chest, abdomen, limbs, etc. Stimulable phosphor sheets used to record such radiation image information are selected in sizes (e.g., a half size) depending on the body parts to be recorded.
There is a recent demand for the diagnosis of entire vertebral columns using a built-in type radiation image information recording and reading apparatus. To diagnose an entire vertebral column using a built-in type radiation image information recording and reading apparatus, the image of the vertebral column may be divided into two portions, which are recorded respectively on two stimulable phosphor sheets. However, the recording process is complex and inefficient since two different parts of the vertebral column must be recorded independently. If the patient moves while the image recording unit is moving after one image has been recorded, then an accurate subsequent image would not be recorded, and hence a correct diagnosis could not be carried out.